A pane of glass is normally mounted in firecode construction in a fire-resistant frame, typically of metal. The outer edge of the glass pane is fitted into a channel of the frame. As described in German patent 2,328,737 filed Jun. 6, 1973 by G. Ortmanns and in German patent document 3,140,785 filed Oct. 14, 1981 by G. Leyens et al, it is standard to interpose a layer of heat-resistant insulation material in the channel on at least one side of the pane, normally on the so-called cold side which is that side on which fire is less likely. The insulation layer prevents the glass pane from pulling out of the frame.
Such an arrangement is only effective for relatively short-duration fires. When, however, the pane is exposed to a fire for a much longer period, for instance 60 min, the glass pane deforms at its edges and comes at least partially out of the channel holding its outer edge.